Lehman who sang two performances of Tristan at the Met last season, for an ailing Ben Heppner.
At press time, Seiffert is still scheduled for performances on Dec. 12, 16, and 20. Daniel Barenboim conducts, with Katarina Dalayman singing the role of Isolde.
The cast also features Michelle DeYoung as Brang‹ne, Gerd Grochowski as Kurwenal and Kwangchul Youn as King Marke.
Curtain time for the 5-hour Wagner epic is 11 AM. For tickets and information, visit The Metropolitan Opera.